Bricks, building blocks, natural and artificial stone are examples only of strong, rigid relatively brittle materials, that are used in construction, and are commonly and extensively used, owing to their economy, versatility and decorative possibilities. The hand laying of these materials is labour intensive, requiring considerable skill and experience to ensure that the resulting structures are mechanically sound, of good appearance, and yet have been produced economically. Stone must often be trimmed at the site, while a time-consuming part of brick and block laying arises at wall corners and door and window openings, where it is often found that partial-length bricks or blocks are required. Owing to manufacturing tolerances in brick or block length, and variations in thickness of the intervening mortar, it usually is not possible to determine beforehand what partial length is required, and this must be measured in situ and cut from the bricks or blocks just before use. There are a number of well established ways in which such cutting has been achieved hitherto.
Perhaps the oldest method employs a special hammer with which the mason scores the brick, block or stone until it breaks along the score line. This requires considerable skill and experience on the part of the mason if a clean, accurate cut is to be obtained, and even with a skilled operative it is very difficult to obtain such a cut, owing to the random brittle structure common to the materials, so that a number of attempts may be required with corresponding waste of time and material. Moreover, it is difficult to obtain a smooth cut, and virtually impossible to obtain thin pieces, owing to the high probability that they will be shattered by the hammer blows.
One type of cutting apparatus specifically designed for this purpose and in common use is a guillotine, in which a cutting blade is forced down on to the body by a motor consisting of a hand-pumped hydraulic cylinder and piston. It requires the cutting location to be marked on the brick or block before insertion into the machine, and is time-consuming because of the slow action of such a pump, and the need to release the pressure and retract the piston to raise the blade when the cut is completed. The apparatus is found to be somewhat uneconomic when used with bricks provided with vertical mortar-receiving keying holes, since as the blade is pressed home the brick tends to break at the holes and not at the intended cut line, so that a number of attempts may be required with a relatively large wastage of time and material. The apparatus is relatively heavy and expensive and is difficult to lift onto and to operate on scaffolding, where the majority of the work usually is done. Motor operation of the pump makes it even heavier and more expensive. If electricity is not readily available at the site then a gasoline-powered generator must also be provided. In another version of such apparatus the cutting blade is forced down on to the body by motor means comprising a lever multiplying the steady cutting force applied by hand by the operator. However, owing to the high compression strengths of these materials, the high cutting force required necessitates very strong and heavy lever structures.
Another apparatus in commercial use is a rotary cutting saw designed specifically for cutting hard, brittle materials and employing an expensive diamond coated blade. These are also heavy and expensive and produce considerable amounts of fine dust so that the operatives need to wear dust masks and the surroundings tend to be coated with the dust. The wastage when used with holed bricks is much less than with the hydraulic or lever operated apparatus, but of necessity they are electric motor driven, with the consequent problem if suitable electric power is not available. They have the added problem that the brick or block must be clamped, or held firmly by hand by the operative, while in frictional contact with the fast moving blade, slowing down its operation or making it more tiring to operate.